Built-in Function Support › Internal Structure Of Built-In Functions

Internal Structure Of Built-In Functions

CA ADS supplied built-in functions and user-defined built-in functions share the same internal structure. This structure consists of the following components.

Master Function Table

The master function table lists the invocation names for each built-in function. The master function table is used during process compilation to associate a coded invocation name with a real (generic) function name and to point to a model XDE (expression description element) module that describes the function.

Model XDE Modules

Model XDE modules contain one or more model XDE tables. Each model XDE table describes a function, including the function's parameters, work area requirements, result field, and processing program name. During process compilation, a model XDE table is used to produce a series of XDEs that form the compiled representation of the function.

XDEs and VSDEs

XDEs and VXDEs describe functions at runtime. XDEs are created during process compilation; one VXDE (variable expression description element) is created for each XDE at runtime to hold variable information.

Processing Program Modules

Processing program modules contain processing logic for one or more functions. At runtime, when the XDEs and VXDEs for the function are processed, the runtime system calls the appropriate program and passes to it all required information. The program executes, then returns control to the dialog.